1. Technological Field
This invention pertains generally to screen content coding in high efficiency video coding (HEVC) systems, and more particularly to base color merging (BCM) within HEVC utilizing a multi-stage base color and index map (MBCIM).
2. Background Discussion
In JCTVC-M0330, a multi-stage base color and index map (MBCIM) has been advanced for screen content coding in Range extension (RExt) for high-efficiency video coding (HEVC). This mode for coding screen content is based on the intra coding framework of the high efficiency video coding (HEVC) standard. In this method a decomposition of each intra predict unit (PU) is first performed into color components and structure components. Afterward, a two-stage prediction scheme is employed to generate two prediction indexes for each pixel to code those structure components.
FIG. 1 depicts, as per the JCTVC-M0330 disclosure, decomposition of a CU input block into colors, for example five colors shown, and composition of the reconstructed block. A structure map is seen with the color numbers for each pixel of the example CU.
As described for MBCIM, screen content refers to computer generated images or videos. This screen content differs from photographic images in two primary regards. (1) Screen content blocks are typically dominated by a limited number of major colors, generally these are significantly different from each other. (2) Block structures found in screen content is generally more complex than found in photographic images. As MBCIM methods progress there is additional need for increasing coding efficiency.
Accordingly, a need exists for further enhancements of MBCIM toward reducing redundancy.